The present invention relates to a method and apparatus for communication switching having a service function, and more particularly, to a switching system having a subscriber state management function which can switch by using identification (ID) numbers and can manage states of subscribers who are in communication, with ID numbers of the subscribers.
A conventional telephone exchange system serves those telephone sets which have their own telephone numbers and connects a calling telephone set with a called telephone set by receiving a telephone number of the called telephone set. In this case, a telephone number corresponds to an accommodation terminal of the switching equipment so that the switching equipment can discriminate connection terminals by merely receiving a telephone number. A calling subscriber is required to call and receive calls at a fixed telephone set in accordance with the conventional telephone exchange system.
In other words, when a calling subscriber dials a telephone number of the other person corresponding to terminal accommodation positional information in the switching equipment, the switching equipment terminates the call to a subscriber line of the terminal accommodation position corresponding to the dialed telephone number, to thereby connect a calling terminal to a called terminal.
Therefore, according to the conventional system, a telephone call is forwarded to a telephone set of a subscriber corresponding to the called telephone number regardless of whether the called subscriber is near the called telephone set or not. If the called subscriber is not near the called telephone set, a third person picks up a telephone receiver to communicate with a calling subscriber and tells the calling subscriber a destination of the called subscriber with whom the calling subscriber wants to communicate, or the like.
The conventional system is extremely cumbersome for a calling subscriber because of the existence of a third person who is not a person with whom the calling subscriber wants to communicate. Further, if the third person does not know the destination of the called subscriber, there is such an inconvenient situation that the calling subscriber cannot communicate with the called subscriber. The conventional system is extremely inconvenient for a called subscriber as well particularly in such a situation when the subscriber expecting a telephone call cannot go out even if he or she wants to do so, because the subscriber must wait for the call to be received at the telephone set which is located at a fixed position. The conventional system is also cumbersome for a third person as well because he or she will have to respond to a telephone call which is not destined to this third person.
As a method for solving the above problems, there has been a personal service of a so-called "follow me" call service according to which a telephone transfer function is provided at the switching equipment or a terminal where a telephone number of a subscriber's destination is registered so that a telephone call to this subscriber is transferred to the registered destination. According to such a method, however, only the transfer function itself cannot respond to all the similar needs of such transfer in the case where only one telephone set is commonly used by a plurality of subscribers. Further, unless a called subscriber does not know a telephone number of the telephone set at his or her destination, the person cannot register a telephone number of the destination.
As methods for solving the above problems, there have been proposed JP-A-63-42558 and JP-A-63-42559, for example. According to the methods described in the above two Japanese Laid-open patent publications, a subscriber is given an ID number which applies to this individual person, and when the subscriber wants a telephone call to him or her to be received at his or her destination, the subscriber registers his or her ID number to the switching equipment from a telephone set at the destination where a call is wanted to be received. By this arrangement, the switching equipment registers the ID number by corresponding it to the registered telephone number. When there is a telephone call from other calling subscriber to the subscriber whose ID number has been registered, the switching equipment forwards the call to the telephone set having the telephone number which corresponds to the registered ID number, so that a trace connection of a call to an individual telephone number becomes possible.
According to the methods described in the above referenced publications, when a calling subscriber inputs an ID number of a called subscriber, the switching equipment discriminates a telephone number corresponding to the ID number which has been registered and forwards the call to a telephone set of the telephone number (hereinafter referred to as a terminal including a data terminal unit and a telephone set). Management of the state of the terminal as to whether the terminal is busy and the like is performed by each terminal unit.
As a result, when a terminal corresponding to an ID number of a called subscriber which has been inputted by a calling subscriber is busy, the switching equipment cannot discriminate whether the called subscriber having the ID number is busy or other subscriber is busy at this terminal. Further, according to the above methods, even if other subscriber is busy at the terminal, the switching equipment just informs the calling subscriber that the other terminal is busy. JP-A-62-179258 has disclosed a technique of managing communication switching which includes an inputting of an ID number of a calling subscriber as well when the calling subscriber makes a telephone call. However, the above problem has not been considered.